1. Field of Invention
This invention relates to the processing of a flow in a pipe, including a slurry having tailings from a mining operation, such as mature fine tailings (MFT) from oil/sands mining; more particularly, this invention relates to a technique for determining information about an injection of a chemical into the flow in the pipe, including flocculation chemicals, as well as for controlling or regulating the injection of the chemical into the flow in the pipe.
2. Description of Related Art
Tailings are the materials left over after the process of separating the valuable fraction from the worthless fraction of an ore, such as oil sands, copper ore, etc.
In the processing of tailings from a mining operation, such as the processing of mature fine tailings (MFT) in the oil sands mining and separation process, the effectiveness of flocculation chemicals added to a pipe flow of MFT slurry is negatively impacted by (locally) high shear stresses. Flocs are formed by coagulation of particles forming larger aggregates which separate more easily from the carrier fluid. Often it is necessary to add surfactants to overcome repulsive electrostatic forces. Flocs are destroyed by mechanical forces, such as shear forces, breaking the relatively weak induced dipole (Van der Waals) forces.
In complex fluids, such as MFT slurries, the relationship between shear rate and shear stress follows from the generalized Newton equation:
  τ  =            -      η        ⁢                  ∂        v                    ∂        r            In this equation the shear rate equals the velocity gradient dv/dr, t is the shear stress and n is the viscosity which may be dependent on the shear rate and or time. Four conceptually different types of rheological behaviour may be present, either in isolation or in combination:                1. Dilatant, where the viscosity increases with increasing rate of shear, often called shear thickening.        2. Pseudoplastic, where the viscosity decreases with increasing rate of shear, often called shear thinning.        3. Thixotropic, where the viscosity decreases with time under a constant rate of shear, often called time thinning.        4. Rheopectic, where the viscosity increases with time under a constant rate of shear, often called time thickening.In all cases, however the shear stress is dependent on the velocity profile. In the case of a direct proportionality between shear stress and shear rate the fluid is said to be Newtonian.        